The present invention relates to a transportation system of a floated-carrier type, and more particularly, to a transportation system, in which a carrier is suspended from a guide rail, in a non-contact manner, and is propelled along the guide rail.
To increase office or factory automation, transportation systems have recently been installed in some buildings. Such systems are used to transport slips, documents, cash, samples, or the like, between a plurality of locations in the buildings.
In order to avoid spoiling the environment of the offices or factories, transportation systems of this type are expected not to produce dust or high levels of noise. Thus, in U.S. Pat. Appl. No. 726,975, now abandoned, filed previously by the inventors hereof, a carrier is kept suspending from a guide rail, in a non-contact manner, by means of an electromagnetic attractive force acting between the carrier and the guide rail, when the carrier is propelled along the guide rail.
In this transportation system, a track supporting a guide rail is installed in correspondence with a path along which the carrier travels, in a factory. A stator for linear induction motors for propelling the carrier are arranged on the track at predetermined intervals. The stator is provided with an inverter which energizes the stator according to travel instruction supplied from a controller (described later). A reaction plate for linear induction motor is mounted on the carrier. Thus, the carrier is received accelerating or decelerating force from the stator, in such a manner that the carrier travels along the guide rail of the track. Various sensors are provided at predetermined positions of the track. Various controllers for controlling the traveling of the carrier based on signals from the sensors are provided to this system. Therefore, the sensors detect a current traveling position of the carrier, a traveling speed of the carrier, the type of carrier, and the like. These detection signals are supplied to the controllers and processed thereby. Carrier travel instructions are supplied from the controllers to the inverter provided on the stator, thereby controlling the traveling of the carrier.
In order to connect the various sensors and the various controllers, a number of signal wires through which electrical signals propagate are necessary. In addition, power wires for supplying power to the stator for the linear induction motors are also necessary. These signal wires and power wires are disposed along the track. A cumbersome operation is required to mount these signal wires and power wires on the track after the track is installed in the factory.
Furthermore, when a travel path of the carrier is changed, not only an old track is removed and a new track is installed but also the signal and power wires must be again mounted on the new track. For this reason, in order to change the travel path of the carrier, a cumbersome operation is required. Therefore, the travel path of the carrier cannot be easily changed.